Tuesday, March 12, 2013

Kicking Kinetosis

Kicking Kinetosis

It was a dark, chilly, and windy morning in
November.I arrived at Morro Bay to fish
for the Collaborative Fisheries Project. The night before, I checked the
swell report, as I am prone to motion sickness, or kinetosis, and unfortunately,
it appeared as though rough seas were ahead.But, with high hopes of somehow overcoming my seasickness with a motion
sickness pill and some ginger root tablets, I boarded the boat the following
morning. After departing from the peaceful bay, I
began to feel a little warm inside. My mouth began to salivate and my body
began to sweat while my stomach started churning, and I was extremely
nauseous.My motion sickness had come
back with a vengeance.All I wanted to
do was lay down and close my eyes, until the boat docked.Not only was this desire to remain
unsatisfied, but I furthermore still had to tag, weigh, measure and release the
catch soon to be reeled in.My miraculous concoction of over-the-counter
motion sickness medication and ginger tablets did not live up to my expectations
and without a moment to find a trash can or even a fishing bucket, I rushed to
the side of the boat and, well, fed the fish.Although I knew everyone was disgusted
watching me hurl over the side of the boat every five minutes, I must say, they
were highly impressed with my multi-tasking skills of projectile vomiting while
gripping a flailing 20-pound lingcod in my hands!

How and why does this happen?So what role does the inner ear (vestibular system) play in all of this, you ask? Well, just as, your muscles, eyes, and skin receptors detect motion or a lack of motion, so too, does your inner ear. The vestibular system (see Figure 2) consists of a semicircular canal system, conveying rotational movements, and otoliths, expressing linear accelerations. Within the semicircular ducts are tiny hair cells called crista, which detect the movement of fluid inside the ear.

In a nutshell, it is caused by the inner
ear (see Figure 1). Overstimulations of the labyrinthine canals of the ear initiate motion
sickness.Motion
sickness occurs when the inner ear, the eyes and other parts of the body that
distinguishes motion, send contradictory messages to the brain.

http://www.directhearingaids.co.uk/index.php/33/how-hearing-balance-work-together/ Figure 1. The three main parts of the ear: external, middle, and inner. The inner ear plays a role in motion sickness.When we move our bodies intentionally, for example,
when we run or jump, the input from all three of these pathways to our brain is
in sync.However, when we experience
unintentional movement, as occurs when aboard a moving fishing vessel, the
input to the brain does not coordinate.During
motion sickness, the brain receives conflicting messages from these numerous
interpreters that express contradictory states of the body’s physical status.For example, on a boat, your feet are not
physically moving, so your joint sensory receptors say to your brain, “I am
still.”However, your eyes perceive the
vanishing shoreline and flowing wake behind the boat indicating movement,
telling your brain, “I am moving.”Similar
to reading a book in the car—your eyes are focused on a stationary page, while
your body registers the movement of the car.And your skin receptors feel wind, as experienced during a fast paced
run, telling your brain, “I am moving.”But your legs and arm muscles are not moving, thus tell your brain, “I
am still.”In other words, you feel
motion, but you don’t see it.Or, you
see motion, but you don’t feel it.Imagine
how you would feel trying to decode these conflicting messages!

Figure 3. (a) The head is positioned straight, the, therefore the cristae are also straight. (b) When the head turns the cristae flex in the opposite direction. Note: fluid inside the inner ear is moving the
cristae.

Motion sickness occurs when our brain receives these
contradictory messages.My personal
encounter with motion sickness was specific to seasickness, which is just one
type of motion sickness. Many people experience the symptoms of motion
sickness traveling in a car, train, airplane, bus, subway or while watching
video games, IMAX movies, or riding roller coasters. While I was on the boat, my inner ears and
skin receptors sent signals to my brain indicating motion. However, my muscle
receptors registered my motionless status as I was standing still, or at times,
sitting still. My eyes were glued to the
floor that wasn’t moving, but as soon as my eyes met the horizon or shoreline,
my eyes sent an opposing signal indicating motion—conflicting with the one sent
just moments ago from the same receptor.

This mismatch of neural signals ultimately, activates
the postrema in the brain, which controls emesis (vomiting), as illustrated in
the figure below (Figure 4).The vomiting-reflex is
controlled in the vomiting center, or the lateral reticular formation, located
in the medulla oblongata at the base of your brain.The link between motion sickness and vomiting
is not wholly understood, but one theory includes the toxin theory.According to this theory, vomiting is a
defense mechanism against neurotoxins.Due to the conflicting signals sent to the brain, the brain interprets
one of them as a hallucination, triggered by poison or drugs.The brain, in turn, instructs the body to
purge itself of these toxins through emesis.

(https://www.healthtap.com/#user_questions/220991-why-do-we-throw-up-when-we-get-motion-sickness)Figure 4. The pathway of the postrema area in the brain, controlling vomitingSo, we now know why we get motion sickness,
but what do we do about it? There are several different remedies to help
alleviate the symptoms, but there is no “cure” per sue.One of the most popular methods, includes the
one that failed to come to my rescue that Saturday morning, over-the-counter
medication.These include drugs like
Dramamine or Bonine.These are
antiemetics, or drugs that inhibit vomiting.These drugs work by blocking the messages of certain neurotransmitters
like serotonin, acetylcholine, dopamine, and histamine.If the brain does not receive information
from these neurotransmitters, it is unable to respond.These antiemetics block the transmission of
information from the vestibular apparatus to the lateral reticular formation
(vomiting or emetic center) in the medulla oblongata.See the figure below (Figure 5) to see the where the antiemetics
can block neurotransmitters’ signal to the vomiting center.

Figure 5. Different pathways of antiemetics blocking neurotransmitters' signals in the vomiting center

But these antiemetics also tend to pack
another punch—extreme drowsiness.The
reason being is because some antiemetics are also antihistamines, like
Dramamine.The main ingredient in antihistamines
that causes drowsiness is called diphenhydramine that fights histamine (as seen
above) by binding to the receptors of specific cells in the body that histamine
would typically bind to otherwise, blocking them from relaying their message. If histamine does not have access to these
receptors, it cannot react on the body.But antihistamines are not solely responsive to histamine receptors, but
acetylcholine receptors as well.If
diphenhydramine clocks an acetylcholine receptor, acetylcholine reuptake no
longer occurs, causing an excess of acetylcholine, and thus drowsiness.

The only medication that I have taken (and I have take a lot) that did not cause this unfavorable side effect is Triptone, which is unfortunately,
no longer being manufactured. Scopolamine patches, placed behind the ear, as
well as, wristbands applying pressure to specific pressure points believed to
alleviate motion sickness, has been successful for many.Ginger root pills or chews can also diminish the
side effects of motion sickness, phenols in ginger also help relax the stomach
muscles, including the pyloric valve; therefore, reducing the activity of the
stomach.Ginger also promotes the stomach
to secrete digestive juices or enzymes, furthermore, neutralizing stomach
acids.Other than these more medicinal aids, a few
words of personal advice...Always have food in your stomach before you travel,
it may help you not get sick and if you do get sick, at least you will not be
throwing up bile..And lastly, carry a
barf bag to avoid some embarrassment.
References:

Karen Naifeh. 1986. Exploratory Studies of
Physiological Components of Motion Sickness: Cardiopulmonary Differences
Between High and Low Susceptibles. National Aeronautics and Space
Administration ARC 275a. Theeuwes, J., A.F. Kramer, S. Hahn, and D.E.
Irwin. 1998. Our eyes do not always go where we want
them to go: capture of the eyes by new objects. Psychological
Science
September 9: 379-385.

1 comment:

Could jumping up & down like a crazy person while on the boat correct these contradictory messages to the brain? If your moving around a lot then not only will your eyes sense movement but the rest of your body will as well. Although, this technique may be just as embarrassing as personally chumming the waters!